During the September Keynote they introduced the new Apple Pencil. In the presentation they showed a quick video of what Apple Pencil could do with apps. One of those apps shown used a straight edge (see https://www.dropbox.com/s/nv23sghkp0u53de/ruler.jpg?dl=0). It can also be seen at marker 30:45 in the Apple Keynote presentation. Does anyone know what app this was that they used?